Currently, a demand for a polyarylene sulfide, a representative engineering plastic, has increased for applications in a variety of electronic goods and products used in high temperatures and corrosive environments due to its high thermal resistance, chemical resistance, flame resistance, and electric insulation.
Polyphenylene sulfide (hereinafter, abbreviated to “PPS”) is the only commercially available polyarylene sulfide. PPS is widely used for housing or major parts of automobile equipment and electric or electronic devices due to its excellent mechanical, electrical, and thermal properties, and chemical resistance.
The primary process for commercially producing PPS is solution polymerization of p-dichlorobenzene (hereinafter, abbreviated to “pDCB”) and sodium sulfide in a polar organic solvent such as N-methyl pyrrolidone, which is known as the Macallum process.
When a polyarylene sulfide is produced by the Macallum process, however, the solution polymerization using sodium sulfide, etc., may produce by-products in a salt form, which requires washing or drying processes, etc., to remove such by-products in a salt form and any residual organic solvents. Further, a polyarylene sulfide produced by the Macallum process has a powder form, which may render the subsequent processes inconvenient and impair its workability (see U.S. Pat. Nos. 2,513,188 and 2,583,941).
To resolve the above problems, a process of manufacturing a polyarylene sulfide such as PPS by melt polymerization of reactants containing diiodide aromatic compounds and elemental sulfur has been suggested. As the process neither produces by-products in a salt form in the manufacture of polyarylene sulfide nor uses organic solvents, it does not require any separate process for removing such by-products or organic solvents. Further, the finally obtained polyarylene sulfide has a pellet form, which may render the subsequent processes convenient and improve its workability.
Meanwhile, conventional PPS has a problem of poor adhesion to metals since a large amount of outgassing (i.e., oligomers of low molecular weights) is generated at the flow front in injection molding, which prevents micropores on the metal surface from being filled when the PPS adheres to metals. As an alternative for improving adhesion of PPS to metals, a resin composition prepared by compounding PPS with a polyolefin containing a polar group and a compatibilizing agent has been suggested. However, it has been found that use of such alloy or oligomer degrades the mechanical properties of PPS and weakens the thermal characteristics of PPS.
Accordingly, it is required to develop a PPS composition having an excellent adhesive property to metals with a reduced amount of outgassing at the flow front, which is an underlying problem in the conventional metal adhesive plastics.